Sen. Mark Warner, a Virginia Democrat, wants the Federal Trade Commission to inspect Facebook's recently-revealed study of its users' emotions and asked the agency to consider whether more stringent guidelines for conducting such research are necessary.

However, at least by one measure -- use of Facebook credentials to login to other websites -- everyday web users have few qualms about maintaining their addictions to the social network and convenient Facebook logins.

Though controversial among privacy wonks and academic researchers, the study and its ethical implications seem to have made little impression on the mainstream public and most Facebook users. Since June 28, when the Facbook research news started to percolate, logins via Facebook account information on non-Facebook sites barely budged, dipping from 43.6% to 43.3%. The data comes from Janrain, which helps clients including Universal Music Group and Dr Pepper manage social logins on their sites, and make use of the information associated with those logins. The company provides quarterly reports on the social platforms people use to login to sites across the web, including Facebook, Google Plus, Twitter and Linkedin.

Some academics have expressed concern over the ethics of a study conducted by Facebook's data scientists who studied the impact of positive and negative posts on around 700,000 users in research conducted in January 2012. The Facebook researchers did not notify people whose posts and news feeds were analyzed for the study, which found that when shown more positive posts on Facebook, people were more positive in their own subsequent posts. In turn, the study found negative posts spurred more negative posts.

"As the collection and analysis of 'big data' continues to increase, and as it assumes a larger role in the business plans of Internet-based companies, it is appropriate that we consider questions about what, if any, oversight might be appropriate, and whether best practices should be developed and implemented by the industry or by the FTC," Mr. Warner wrote in his missive sent to FTC commissioners July 9.

The familiar "Sign in with Facebook" button is ubiquitous online. The convenience of using authentication from Facebook, Google and other accounts to register with websites is enough for most people to sacrifice some privacy in exchange for a more seamless web experience. Meanwhile, publishers -- from ecommerce sites to news outlets and music services -- have enabled the quick signup functionality on their sites, in part because it's easier than convincing people to establish yet another account exclusive to just one site.

Perhaps even more enticing: There's a wealth of data available via those big blue buttons. When sites enable logins from platforms such as Facebook and Google, they create deep data connections between their own sites and those login sites. For instance, according to Janrain, more than 95% of Universal Music Group logins are enabled through other social platforms. And the music label takes advantage of that data. With the help of Janrain, Universal knows the bands and artists fans like on Facebook or follow on Twitter, and employs that data to determine which of its own artists are similar, then recommends them via the site or through emails.

As the data links between Facebook logins and web behavior become more entrenched, the drumbeat of questions surrounding the company's ethical standards for employing that data are bound to remain steady.

In his letter to the FTC, Mr. Warner said that while he is "not convinced that additional federal regulation is the answer," he has "concerns about whether or not Facebook responsibly assessed the risks and benefits of conducting this behavioral experiment as well as the ethical guidelines, if any, that were used to protect individuals."